The pen boards in the fish hold extended to about 0.3 m below the deckhead, but the catch was reportedly evenly distributed in the hold. Therefore, it is likely that the heavy list and settling by the stern, which occurred after the sudden swamping of the afterdeck, would have been experienced regardless of the type of fish being carried. It was calculated that, with the freeing ports under water, the afterdeck could contain some 20 tonnes of water. The non-watertight hatch to the fish hold would allow the water shipped on the afterdeck to enter that compartment. This, together with the downflooding of the engine compartment and the cuddy, would overcome the vessel's reserve buoyancy.Analysis The pen boards in the fish hold extended to about 0.3 m below the deckhead, but the catch was reportedly evenly distributed in the hold. Therefore, it is likely that the heavy list and settling by the stern, which occurred after the sudden swamping of the afterdeck, would have been experienced regardless of the type of fish being carried. It was calculated that, with the freeing ports under water, the afterdeck could contain some 20 tonnes of water. The non-watertight hatch to the fish hold would allow the water shipped on the afterdeck to enter that compartment. This, together with the downflooding of the engine compartment and the cuddy, would overcome the vessel's reserve buoyancy. The vessel was swamped by two heavy confused seas from a direction not consistent with the weather pattern. The non-watertight cover on the fish hold hatch contributed to the sudden sinking of the vessel as the fish hold filled with water when the afterdeck was under water. Downflooding also occurred through the unsecured openings to other under-deck compartments. The NANCYPAULA lost all reserve buoyancy and sank.Findings The vessel was swamped by two heavy confused seas from a direction not consistent with the weather pattern. The non-watertight cover on the fish hold hatch contributed to the sudden sinking of the vessel as the fish hold filled with water when the afterdeck was under water. Downflooding also occurred through the unsecured openings to other under-deck compartments. The NANCYPAULA lost all reserve buoyancy and sank. The NANCYPAULA sank quickly when she lost all reserve buoyancy after two heavy seas filled her afterdeck with water which downloaded into the fish hold and other under-deck compartments.Causes and Contributing Factors The NANCYPAULA sank quickly when she lost all reserve buoyancy after two heavy seas filled her afterdeck with water which downloaded into the fish hold and other under-deck compartments.